This invention relates generally to devices for use in properly aligning the rear end of a vehicle, and particularly devices of this type which are used for aligning the rear end of a race car.
As is well known, if the rear end of a vehicle is misaligned relative to the frame of the vehicle, problems are created in terms of the handling of the vehicle and tire wear. When misalignment of the rear end occurs in race cars, the problems are exacerbated by the high speed at which the vehicle travels, and even a variance of 1/4-inch can create major problems.
Accordingly, it is important that the rear end of a vehicle be precisely aligned, and several prior art devices have been used to assist in obtaining as precise an alignment as possible. One such device includes two stanchions having a string extending generally horizontally therebetween, and this device is set up so that the stanchions are placed alongside of the vehicle with the horizontal string extending generally parallel to the side of the frame of the vehicle. Several vertical strings are then hung from the horizontal string at spaced intervals along the length thereof and a small weight is attached to the lower end of the vertical strings to maintain them at their vertical disposition. A measurement is then made from each of the spaced vertical strings to the frame, and to the extent there is any difference in these measurements indicating misalignment of the rear end, some adjustment is made in the position of the rear end in relation to the frame. While this device provides some assistance in properly aligning the rear end, it has several disadvantages, including some inherent inaccuracy resulting from the use of three or more strings, and the fact that it takes a considerable amount of time (e.g., thirty minutes) to set the device up for use. Also, each time some adjustment is made in the rear end, the position of the device must be reestablished before a second set of measurements can be made.
Another known device includes a longitudinally extending narrow plate that is mounted on wheels at its ends and a beam generator is mounted on the plate to direct a linear laser beam in a direction parallel to the extent of the narrow plate. In use, the device is rolled up to a location adjacent one of the rear tires of the vehicle, and one edge of the plate is pressed against the side wall of the bottom of the tire. With the device in this position, the beam generator is then turned on to generate a beam that extends along the side of the frame of the vehicle, and measurements are made at spaced intervals along the length of the frame to determine the distance between the side of the frame and the beam. To the extent that these measurements are different from one another, they indicate misalignment of the rear end, and adjustments are then made in the position of the rear end and the aforesaid procedure is repeated until the measurements are equal to one another.
While this device is a substantial improvement over the above-described string device, it also has a problem in terms of accuracy. More specifically, the position of the beam relative to the frame is dependent upon the position of the narrow plate which, in turn, is dependent upon the surface configuration of the side of a vehicle tire. Because of the geometry of the path of the beam, even a 1/8-inch variance of the side wall of the tire can result in a 1/2-inch variance at the far end of the beam from a true line indication of the actual position of the rear end relative to the frame. Since even a 1/4-inch variance in the proper alignment of the rear end can create major problems in a race car, as discussed above, the potential for inaccuracy from this device is a serious drawback, and this drawback is compounded by the fact that the wheel of the vehicle on which the tire is mounted may include a further variance in the form of tire "wobble".
The present invention provides a device and method of use which overcomes the above-discussed known devices and which permits the rear end of the vehicle to be precisely aligned in a short period of time.